Tuesday 27 October 2009 07.05 EDT
First published on Tuesday 27 October 2009 07.05 EDT

Michael Jackson fans have launched a campaign suggesting forthcoming documentary This Is It airbrushes the declining health of the singer in his final days.

A website, This Is Not It, suggests Jackson was so frail on the night before he died that 20 fans who regularly followed him penned a letter to the star urging him to take more care of himself.

The fans blame AEG, the promoter of the singer's abandoned London residency, Sony Pictures and Jackson's own entourage for exploiting him for their own financial gain. They are planning to protest with leaflets and flyers at premieres taking place around the world later today and tomorrow.

This Is It, directed by High School Musical's Kenny Ortega, shows Jackson rehearsing at the Staples Centre in LA in advance of this summer's planned dates at London's 02 Arena. Jackson died following a heart attack on 25 June before the tour began.

Talin Shajanian, from Los Angeles, who had been following Jackson since 2003, often waiting with others outside the venues where he was rehearsing, told the BBC the singer was "unusually thin" the last time she saw him.

"A couple of weeks before he passed, we saw him change drastically," she said. "He shared this with us, the pressure that he felt, the concerns that he had."

"He specifically said he was only one person and only had a certain amount of energy to give, that so much was expected of him for these shows. We were expecting him to bulk up, to put on weight for the concerts like he had in the past, and that wasn't happening."

Fans on the This Is Not It website have expressed their scepticism about the project: "The true state of Jackson's failing health was hidden from you by those who are making a profit from the screening of the This is It movie.

"In the weeks leading up to Jackson's death, while this footage was being shot, people around him knew that he looked like he might have died. Those who stood to make a profit chose to ignore it. Friends and fans who had no financial interest, chose to address it and attempted to help him.

"AEG, the promoters for This Is It, ignored the signs, ignored the pleas, and in fact, actively covered up the truth. What you will see on that screen is part of that cover up."

Ortega recently said of Jackson: "Was he slight? Yes. Was he frail? At times. But we had a very strong and excited, happy and determined Michael. He wanted to do this more than anything he's ever wanted to do … That's the truth. It really is."

The film has met with advance praise from Jackson's friend, the film star Elizabeth Taylor, who called This Is It as "most brilliant piece of film-making I have ever seen" following a private screening.

She added, in a lengthy series of Tweets: "It cements forever Michael's genius in every aspect of creativity. He cradles each note, coaxes the music to depths beyond reality. I wept from pure joy at his God-given gift. I truly believe this film should be nominated in every category conceivable."

An autopsy earlier this month found that the 50-year-old star was "fairly healthy" before his death, a coroner having ruled in August that Jackson was killed by the drug Propofol and the sedative Lorazepam.

A statement from Sony Pictures, which is releasing the film, said: "This Is It is a celebration of Michael and his music and the film will demonstrate to fans around the world that he was an artist like no other who was passionately creating a one-of-a-kind concert experience."

"We believe his fans will be grateful for the rare opportunity to see Michael's creativity in action as he prepared and rehearsed for his London concerts."